1. Technical Field
The present invention belongs to the technical field of non-volatile memories and relates to a resistive random access memory structure and a manufacturing method thereof, in particular to a resistive random access memory structure with an electric-field strengthened layer and a manufacturing method thereof.
2. Description of Related Art
Along with the continuous scaling of the integrated circuits, the traditional flash non-volatile memories cannot be shrinked limitlessly as in the development of integrated circuit technology, and the flash memory process is having difficulty breaking through the bottleneck of 45 nm; besides, dynamic and static memories are susceptible to data loss after power failure. In recent years, rapid progresses have been made in various new non-volatile memories, for example: ferroelectric random access memories (FRAM), magnetic random access memories (MRAM), phase-change random access memories (PRAM) and resistive random access memories (RRAM).
Among those memories, information reading and writing of the resistive random access memory is realized by reading or changing the resistance of the resistive switching materials. The resistive switching materials have a high-resistance and low-resistance state. RRAM stores information via the material switching between a high impedance state and a low impedance state. FIG. 1 illustrates a sectional view of a typical RRAM. In this RRAM unit 100, a resistive switching storage layer 102 is located between a top electrode 101 and a bottom electrode 103. The top electrode 101 and the bottom electrode 103 are usually made of metal materials such as Pt and Ti with stable chemical properties, and the resistive switching storage layer 102 is usually made from binary or ternary metallic oxides such as TiO2, ZrO, Cu2O and SrTiO3. The resistance of the resistive switching storage layer 102 is capable of being switched between two states, namely a high impedance state and a low impedance state, which can be represented by “0” and “1” respectively, by the action of external voltage. By the effect of different external voltages, the resistance of the resistive random access memory is capable of being switched between the high impedance state and the low impedance state, to realize information storage.
Along with the further development of integrated circuit technology, a great amount of materials with resistive switching properties have been reported in succession, such as SiO2, NiO, CuxO, TiO2, HfOx and ZrOx. RRAM has attracted great attention because of its advantages such as simple preparation, high storage density, low operation voltage, high reading speed, long keeping time, non-destructive reading, low power consumption, and high compatibility with the traditional CMOS process; and therefore is taken as one of the high-quality candidates for the next “universal” memory.
The stability of the working performance of RRAM, comprising the stability of the writing and erasing voltages and the stability of the signal intensity ratio of the high impedance to the low impedance, is the key factor to make RRAM practical. Usually, RRAM faces the major problems of unstable erasing voltage and unstable erasing current. Therefore, seeking methods for preparing the highly stable RRAM with optimized performance has become a key measure for allowing RRAMs to be applied in the industry.